Date: Fri, 27 Mar 2020 20:16:32 -0500
From: Justin Pryzby <pryzby@telsasoft.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Masahiko Sawada <masahiko.sawada@2ndquadrant.com>,
	Alvaro Herrera <alvherre@2ndquadrant.com>,
	Andres Freund <andres@anarazel.de>,
	Michael Paquier <michael@paquier.xyz>, pgsql-hackers@postgresql.org
Subject: Re: error context for vacuum to include block number
Message-ID: <20200328011632.GY20103@telsasoft.com>
References: 
 <CAA4eK1L33gvQ1z-CHctzTWng2HfmFn0cDJif_mpBOvG47Mymow@mail.gmail.com>
 <CA+fd4k61uPzeAWT1EZOwPWq7DkhgVTrC_wmUNCzVW+MbP9Wjfg@mail.gmail.com>
 <20200326150457.GB17431@telsasoft.com>
 <20200326221752.GR17431@telsasoft.com>
 <CAA4eK1+b5-aJcbpvqCFB7Qi0zLKTZNJmA+Js644M2YeiEyTZtw@mail.gmail.com>
 <20200327044424.GD20103@telsasoft.com>
 <20200327061601.GE20103@telsasoft.com>
 <CAA4eK1LKYnDV8bcx59TdR5-s2Cfk75g_wfAjRyy-cL8S+WvHXw@mail.gmail.com>
 <20200327190428.GS20103@telsasoft.com>
 <CAA4eK1LuHowu1Gm++_miME9RSL0OiuqMpK_K-L0SqDaxJEKMcg@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: 
 <CAA4eK1LuHowu1Gm++_miME9RSL0OiuqMpK_K-L0SqDaxJEKMcg@mail.gmail.com>
User-Agent: Mutt/1.9.4 (2018-02-28)
Precedence: bulk

On Sat, Mar 28, 2020 at 06:28:38AM +0530, Amit Kapila wrote:
> > Hm, but I caused a crash *without* adding CHECK_FOR_INTERRUPTS, just
> > kill+sleep.  The kill() could come from running pg_cancel_backend().  And the
> > sleep() just encourages a context switch, which can happen at any time.
> 
> pg_sleep internally uses CHECK_FOR_INTERRUPTS() due to which it would
> have accepted the signal sent via pg_cancel_backend().  Can you try
> your scenario by temporarily removing CHECK_FOR_INTERRUPTS from
> pg_sleep() or maybe better by using OS Sleep call?

Ah, that explains it.  Right, I'm not able to induce a crash with usleep().

Do you want me to resend a patch without that change ?  I feel like continuing
to trade patches is more likely to introduce new errors or lose someone else's
changes than to make much progress.  The patch has been through enough
iterations and it's very easy to miss an issue if I try to eyeball it.

-- 
Justin